Re: [Amel] 24 Volt Alternator charger


The field coil on the 24V alternator has to be supplied with voltage before it will generate power. The 12V alternator gets its field power from the starter battery via the starter switch. The configurations are all slightly different but SM 331 got power for the 24V field coil from the house batteries via a relay. The relay was triggered by 12V coming from the starter switch. It is likely that this relay is bad on your setup. You can test this by metering the 24 volt field coil contacts on the alternator - after turning on the starter switch "power" (so that the lights / meters come on) but before hitting the starter. You should have 24V power to the alternator. Check the voltage. If it is low you may have a dirty connection somewhere. BTW, to prevent overcharging during long periods of motoring in hot conditions, you can just disconnect the field coil wires before starting the engine and there will be no power output from the alternator. To begin charging while the engine is running, you just reconnect the field coil.
Fair Winds,
Ed Steele

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